Oil-and water-resistant fabrics and method for their production



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April 24, 1962 L. SEGAL ETAL OIL AND WATER-RESISTANT FABRICS AND METHODFOR THEIR PRODUCTION Filed Aug. 1, 1958 Perfluoromono-corboxylic Add orSch Aluminum or Zirconium Sul'i INVENTORS LEON SEGAL LEOPOLD LOEB VERNEW. TRIPP ROBERT L. CLAYTON, JR.

ATTORNEY United States Patent ()fifice 3,031,335 Patented Apr. 24, 1962OIL- AND WATER-RESISTANT FABRICS AND METHOD FOR THEIR PRODUCTION LeonSegal, Metairie, La., Leopold Loeb, Louisville, Ky., and Verne W. Tripp,Marrero, and Robert L. Clayton, Jr., Metairie, La., assignors to UnitedStates of America as represented by the Secretary of Agriculture FiledAug. 1, 1958, Ser. No. 752,683 18 Claims. (Cl. 117-69) (Granted underTitle 35, US. Code (1952), see. 266) A non-exclusive, irrevocable,royalty-free license in the invention herein described, throughout theworld for all purposes of the United States Government, with the powerto grant snblicenses for such purposes, is hereby granted to theGovernment of the United States of America.

application is a continuation-impart of application Serial No. 663,857,filed June 5, 1957, now abandoned.

This invention relates to stain-resistant fabrics and to a process forproducing them. More particularly, it relates to and has the objectiveof the production of cellulosic fabrics which are resistant to soil,grease, oil, and water borne stains.

It is known that hydrophobic and oleophobic surfaces can be produced bydepositing on a base a monolayer of a chromium coordination complex of afluorocarbon acid.

According to this invention, textile fabrics of improved waterandoil-repellency are produced by a two-step process involving theimmersion of the fabric in a solution of a salt, such as, aluminumacetate, zirconium nitrate, or zirconium butoxide, drying the fabric,and then immersing the dried fabric in a solution of aperfiuoromonocarboxylic acid, such as perfiuoro-octanoic acid,perfluorodecanoic acid, or one of their salts, In a prefer-red form, theinvention involves the use of the acid dissolved in a highly polarsolvent, such as, ethanol.

The resultant product, where a cellulosic fabric is treated, isrepellent to both oil and water and is thus highly resistant to water,oil, and grease-borne soil and stains. This effect is due to thepresence on the cellulose fiber of an activated substrate (the residueof the water soluble salt) which attracts the carboxylic end' of theacid molecule, leaving a highly oriented surface of CF groups which areboth oleophobic and hydrophobic.

The single FIGURE of the drawing shows an exaggerated view of atransverse cross section of a fiber treated according to this invention.As illustrated, the fiber has a first coating of an aluminum orzirconium salt and a coating, over the first one, of theperfluoromonocarboxylic acid or one of its salts.

Where an acidic salt, such as, zirconium nitrate, is used, it isdesirable to neutralize the acidity before treating the fabric with theperfluoro acid. This is accomplished by immersing the fabric, which hasbeen partially dried after treating with the salt solution, in analkaline solution, such as for example, aqueous ammonia, followed bydrying of the neutralized fabric.

The invention is further illustrated by the following examples:

Example 1 A sample of bleached 80 square cotton fabric was steeped in a1.0 normal aqueous solution of aluminum acetate. After removal from thebath, the impregnated fabric was airdried. A portion of the dried fabricshowed a slight degree of hydrophobicity, but no oil-repellency. Asecond portion of the dried fabric was put aside for use in Example 2,below.

The remaining .dried fabric was immersed for a period of less than 30seconds in a 0.5% solution of perfiuoro- 2 decanoic acid in alcohol andagain air-dried. After drying, the perfluorodecanoic acid treated fabricwas found to be extremely hydrophobic and oleophobic according to thetests described in Example 2, below.

Example 2 (a) Drops of water and of mineral oil were placed on theportion of the dried, aluminum acetate impregnated fabric which was setaside in Example 1. The oil spread and penetrated the body of thefabric, indicating no oleophobic properties. The water drops initiallyassumed a spherical shape, indicating a high contact angle at thesolid-liquid interface. However, after a few moments, the water dropsalso spread and penetrated the body of the fabric, indicating poorwater-repellency.

(b) Drops of water and mineral oil were placed on portions of the driedfabric after the treatment with perfluorodecanoic acid. The drops ofwater remained spherical for a number of hours until they evaporated,while the drops of mineral oil remained spherical indefinitely.

These tests indicate the great waterand oil-repellency produced by thetwo-step treatment, and also that the hydrophobic effect is not producedby the presence of basic aluminum salts, aluminum hydroxide, andaluminum oxide which are essentially hydrophobic materials.

Example 3 The same procedure as Example 1 was followed except that a 0.2normal aqueous solution of the aluminum salt was used in the first step.This sample showed substantially the same oiland water-repellency asthat of Example 1.

Samples prepared according to Examples 1 and 3 were soiled withsynthetic (simulated natural) and also with dry (carbon particle) soilsby tumbling in a laboratory soiling device. The soil resistance wasevaluated by measuring the light reflectance of these samples as compared with an unsoiled control and a similarly soiled, untreatedcontrol. The reflectance of the unsoiled con trol was found to be 92%.When synthetic soil was used this value dropped to 34% for the untreatedsample. Both the treated samples dropped only to 56%. When dry soil wasused the control soiled to a reflectance of 36%; that of sample 2 was52% while that of sample 1 was 58%.

Example 4 In order to minimize the possible degrading effect on thefabric by aluminum acetate, the same procedure as in Example 3 wasfollowed except that 1.5 equivalents of sodium acetate were incorporatedinto the alcoholic per-fluorodecanoic acid solution. A sample treated inthis manner has substantially identical oil, water, and soil resistanceas that described for the preceding example. The heat degrading propertyof the sample was evaluated by heating it for 24 hours at degrees C. Anuntreated control subjected to this degree of heat exposure lost 11% ofits strength as measured on a standard laboratory fabric breakingstrength tester. A sample treated with 0.2 normal aluminum acetate alonelost 45% of it sstrength. However the sample treated in the mannerdescribed in thisexample suffered a loss of only 20%.

Example 5 The same procedure as Example 1 was followed except that anaqueous solution of 5% zirconium nitrate was used in place of thealuminum acetate solution, and the fabric was neutralized after partialdrying by brief immersion in a 0.7% aqueous ammonia solution withsubsequent removal and drying. Samples treated in this manner hadsubstantially the same oil, water, and soil resistance as thosepreviously described.

3 Example 6 Cotton sheeting was padded to as close to 100% Wet pickup aspossible with aqueous 0.5, 0.25, and 0.1 molar aluminum acetatesolutions. The aluminum acetate was prepared by double decomposition ofaluminum sulfate and barium acetate. After air-drying, the impregnatedfabrics were padded with 1% perfiuorooctanoic acid solution (made upwith 95% ethyl alcohol) to as close to 100% wet pick-up as possible(usually 80-90%), airdried, then heated in a forced draft oven at 110 C.for 30 minutes. The dry fabrics were repellent to oils and water.Similar treatments were applied to cotton print cloth with similarresults. Treated cotton sateen and treated cotton-rayon whipcord showedlow repellency. Material treated with 0.5 molar aluminum acetate alonewas not oilor water-repellent.

Example 7 Excellent repellency to oils was obtained by using a solutionof perfluoro-octanoic acid on cotton sateen and cotton-rayon whipcordimpregnated with 0.5 molar aluminum acetate as in Example 6.

Example 8 0.5 and 1.0% for the perfiuoro-octanoic acid failed to bestowany oil-repellency.

Example 9 Qualitative filter paperwas immersed in solutions made bytaking aqueous 0.5 molar aluminum acetate solution in equal volumes with1%, 0.5%, and 0.1% alcoholic perfluoro octanoic acid solutions andair-dried or ovendried. The treated filter papers were repellent to oilsand water placed on the surfaces. Substitution of perfiuorobutyric acidfailed to bestow oil-repellency. The 0.5 molar aluminum acetate and the1% perfiuoro-octanoic acid solutions in volume ratios of 1:1 and 1:4,respectively, were boiled down to a thick white solution or a white waxypaste which was smeared on the filter paper, followed by airandoven-drying. The treated filter papers were highly repellent to oils andwater. Oil failed to spread on the surface of the stainless steel bladewhich was coated with the dried paste, although a drop spread rapidly onan uncoated portion.

Example 10 The clear solution that resulted when 5% zirconium butoxidein isopropanol (prepared by dilution of 50% zirconium butoxide inbutanol and stabilized against decomposition by atmospheric moisture byinclusion of acetonyl acetone) was mixed in equal volume with 1%perfiuoro-octanoic acid in isopropanol was applied to qualitative filterpaper which was then airand over-dried. The treated paper was highlyrepellent to oils and water. Whereas untreated filter paper becamesoaked and had little strength when water was applied, the treated papersimilarly exposed to water was not wetted and retained high strength.

We claim:

1. Theprocess for producing a fabric resistant to soil, grease, oil, andwater-borne stains which comprises immersing the fabric in a solution ofa salt selected from the group consisting of aluminum acetate, zirconiumnitrate and zirconium butoxide, drying the fabric, and immersing thedried fabric in a solution of perfiuorodecanoic acid to produce on thefibers of said fabric an active substrate having attracted thereto thecarboxyl end of the molecule of said perfiuorodecanoic acid, therebyproviding a highly oriented surface of CF groups which is bothhydrophobic and oleophobic.

2. The process of claim 1 wherein the solution of the salt is an aqueoussolution of aluminum acetate.

3. The process of claim 1 wherein the solution of the salt is an aqueoussolution of zirconium nitrate.

4. The process of claim 1 wherein the perfiuorodecanoic acid isdissolved in a highly polar organic solvent.

5. The process of claim 4 wherein the organic solvent is ethanol.

6. The process for producing a fabric resistant to soil, grease, oil,and water-borne stains which comprises immersing the fabric in anaqueous solution of aluminum acetate, drying the fabric, and thenimmersing the fabric in a solution containing sodium acetate andperfiuorodecanoic acid to produce on the fibers of said fabric an activesubstrate having attracted thereto the carboxyl end of the molecule ofsaid perfiuorodecanoic acid, thereby providing a highly oriented surfaceof -CF;, groups which is both hydrophobic and oleophobic.

7. The process for producing a fabric resistant to soil, grease, oil,and water-borne stains which comprises immersing the fabric in anaqueous solution of zirconium nitrate, neutralizing the fabric in adilute aqueous alkaline solution, and treating the neutralized fabricwith a solution of perfluorodecanoic acid to produce on the fibers ofsaid-fabric an active substrate having attracted thereto the carboxylend of the molecule of said perfiuorodecanoic acid, thereby providing ahighly oriented surface of CF groups which is both hydrophobic andoleophobic.

8. The process for producing a fabric resistant to soil, grease, oil,and water-borne stains which comprises immersing the fabric in anaqueous solution of zirconium nitrate, partially drying the fabric,neutralizing the partially dried fabric with a dilute aqueous alkalinesolution, drying the neutralized fabric and then immersing the fabtie ina solution of perfiuorodecanoic acid to produce on the fibers of saidfabric an active substrate having attracted thereto the carboxyl end ofthe molecule of said perfiuorodecanoic acid, thereby providing a highlyoriented surface of CF groups which is both hydrophobic and oleophobic.

9. The process of claim 8 wherein the dilute aqueous alkaline solutionis a solution of ammonium hydroxide.

10. The process for producing a fabric resistant to soil, grease, oil,and water-borne stains which comprises immersing the fabric in asolution of a salt selected from the group consisting of aluminumacetate, zirconium nitrate, and zirconium butoxide, drying the fabricand immersing the dried fabric in a solution of perfluorooctanoic acidto produce on the fibers of said fabric an active substrate havingattracted thereto the carboxyl end of the molecule of saidperfiuoro-octanoic acid, thereby providing a highly oriented surface of--CF;, groups which is both hydrophobic and oleophobic.

11. The process of claim 10 wherein the solution of the salt is anaqueous solution of aluminum acetate.

12. The process of claim 10 wherein the solution of the salt is anisopropanol solution of zirconium butoxide.

13. A soil, grease, oil, and water-stain resistant fabric having thesurface of the fibers thereof coated with an active substrate comprisinga salt selected from the group consisting of aluminum acetate, zirconiumnitrate, and zirconium butoxide and a coating on said salt of a compoundselected from the group consisting of perfluorooctanoic acid,perfluorodecanoic acid, and salts thereof wherein the carboxyl ends ofthe molecules of said compound are attracted to said active substrate,thereby providing a highly oriented surface of -CF groups which is bothhydrophobic and oleophobic.

14. The fabric of claim 13 wherein aluminum acetate is coated withperfluoro-octanoic acid.

15. The fabric of claim 13 wherein aluminum acetate is coated withperfluorodecanoic acid.

16. The fabric of claim 13 wherein zirconium nitrate is coated withperfluorodecanoic acid.

17. The fabric of claim 13 wherein zirconium butoxide is coated witheperfluoro-ootanoic acid.

18. A process for producing a fabric resistant to soil, grease, oil, andwater-borne stains which comprises immersing a fabric ina solution of asalt selected from the group consisting of aluminum acetate, zirconiumnitrate, and zirconium butoxide, drying the fabric, and immersing thefabric in a solution of perfluoromonocarboxyl compound selected from thegroup consisting of perfluoroootanoic acid, perfluonodecahoic acid, andsalts thereof to produce on the fibers of said fibric an activesubstrate having attracted thereto the carboxyl end of saidperfiuoromonocarboxyl compound, thereby providing a high 1y orientedsurface of -CF;; groups which is both hydrophobic and oleophobic.

References Cited in the file of this patent UNITED STATES PATENTSSchroeder Nov. 3, Doser Feb. 27, Schwartz Mar. 25, Edelstein July 6,Diesslin et a1. Sept. 4, Figdor Apr. 14, Reid Dec. 15,

FOREIGN PATENTS Great Britain Apr. 18,

1. THE PROCESS FOR PRODUCING A FABRIC RESISTANT TO SOIL, GREASE OIL, ANDWATER-BORNE STAINS WHICH COMPRISES IMMERSING THE FABRIC IN A SOLUTION OFA SALT SELECTED FROM THE GROUP CONSISTING OF ALUMINUM ACETATE, ZIRCONIUMNITRATE AND ZIRCONIUM BUTOXIDE, DRYING THE FABRIC, AND IMMERSING THEDRIED FABRIC IN A SOLUTION OF PERFLUORODECANOIC ACID TO PRODUCE ON THEFIBERS OF SAID FABRIC AN ACTIVE SUBSTRATE HAVING ATTRACTED THERETO THECARBOXYL END OF THE MOLECULE OF SAID PERFLUORODECANOIC ACID, THEREBYPROVIDING A HIGHLY ORIENTED SURFACE OF -CF3 GROUPS WHICH IS BOTHHYDROPHOBIC AND OLEOPHOBIC.